Multi-Chamber System Serving as a Liquid Equalizing Tank, and Use Thereof

ABSTRACT

A multi-chamber system serves as a liquid equalizing tank that is suitable, by way of example, for use in a cooling system. In the novel multi-chamber system, a liquid expansion tank is provided due to the arrangement of the chambers and pipe systems whereby preventing external gases from entering the liquid system and enabling it to also be used in accelerated systems, such as a vehicle since no leveled out liquid columns are used. This makes it possible to provide a system for monitoring a volume of gas in a liquid-filled installation that, in addition to the multi-chamber system, also contains a Buchholz relay in the cooling liquid system. The use of this system for monitoring a volume of gas is thus suitable for means of transportation.

Electrical components, in particular transformers, are protected fromthermal overheating during operation by means of liquid cooling circuitssuch as, for example, oil circuits. The transformer oil expands as aresult of being warmed, and is collected above the transformer via anoil line in an oil expansion tank which is also partially filled withtransformer oil. A so-called Buchholz relay is often arranged in the oilline between the oil expansion tank and the transformer, the Buchholzrelay measuring the gas which forms in the transformer and triggering ashutdown of the transformer if a predefined gas volume is exceeded. Alarge gas volume is a common indicator of a fault within thetransformer. For the operation of an oil-cooled transformer, the Germanindustry standard DIN 42566 prescribes that a warning signal istriggered by means of a Buchholz relay if a predefined gas volume isexceeded within the installation. Here, it is detected within theBuchholz relay as a corresponding expansion tank and gas collectingcontainer, which is connected upstream of an actual liquid expansiontank, whether the predefined gas volume has been reached.

In the known systems, air is also sucked from the environment through aventilation opening in the oil expansion tank as the transformer oil iscooled, and the moisture in the ambient air is reduced by means of anair dehumidifier. The infiltration of air or moisture into the coolingcircuit is to be avoided in any case, since this considerably reducesthe dielectric strength of the transformer.

DE 196 36 456 A1 discloses a device for keeping foreign gas out ofsystems having volumes which change as a function of temperature, inparticular electrical transformers, connected to an integrated devicefor influencing a pressure as a function, or independently, of thetemperature of the insulating liquid. The invention described in saiddocument has an expansion tank which is such that a diaphragm isarranged between the insulating liquid and the ambient air or a gascushion, said diaphragm preventing a direct exchange between the ambientair and the cooling circuit.

GB318397 discloses an expansion tank for transformers in which anelastic diaphragm in the expansion tank separates the liquid surfacefrom a gas cushion and therefore prevents an exchange of air with theambient air.

A disadvantage of said known prior art is that, in the event of anexcessive rise in the gas volume within the transformer, there is noshutdown mechanism, since the above described systems are designed onlyfor a completely liquid-filled cooling circuit.

GB368264 describes an expansion tank for transformers in which amulti-chamber system, in which the chambers are arranged so as to bestepped relative to one another, prevents an infiltration of the ambientair into the cooling circuit. A disadvantage with this is, however, thatsaid system functions only in a static intertial system, since anacceleration of the expansion tank could move the liquid columnsrelative to one another and an infiltration of ambient air into thecooling circuit would therefore be possible.

An object of the present invention is to avoid the abovementioneddisadvantages of the prior art and to provide an expansion tank whichcan also be operated in a system which is subject to acceleration.

The object is achieved by means of the invention described in claim 1.Here, it is provided according to the invention that in a first chamber,a first pipeline system connects the first chamber to a liquid system,and a second pipeline system connects the first chamber to at least onefurther, second chamber, the second pipeline system being arranged inthe second chamber in such a way that, when liquid is present in thesecond chamber, the liquid pressure generated as a result is likewisepresent in the second pipeline system, and the second pipeline systembeing arranged in the first chamber in such a way that the secondpipeline system is likewise completely filled with a liquid, and ahydraulic connection is therefore produced between the liquid system andthe second chamber, only when the first chamber is completely filledwith a liquid. The infiltration of ambient air or gases into the liquidsystem via the second chamber is likewise prevented in this case whenthe first pipeline system is completely filled. The opening of thesecond pipeline system is advantageously arranged in the upper region ofthe first chamber.

It is also advantageous for at least one diaphragm in the second chamberto sealingly close off the surface of the liquid from the gas phase inthe second chamber. According to a further preferred embodiment of theinvention, the first chamber is arranged within the second chamber, thechambers being rotationally symmetrical, and the surface of the liquidin the second chamber being sealingly closed off from the gas phase inthe second chamber by means of a rotationally symmetrical diaphragm.Said arrangement of the chambers allows one individual diaphragm, forexample in the shape of a ring, to be used. The diaphragm is preferablyelastic.

Brackets on the inner wall of the second chamber advantageously fix thediaphragm. Alternatively, guide rails, which provide sealing closure, onthe inner wall of the second chamber guide the diaphragm correspondingto the liquid surface in the second chamber. In said arrangement, themechanical loading of the diaphragm is reduced in comparison to a rigidfixing.

The cross sections and/or the heights of the pipeline systems arepreferably designed and configured as a function of the maximum possibleliquid pressure in the first chamber. An air dehumidifier reduces themoisture in the gas phase in the second chamber so that the upper sideof the diaphragm is not chemically or physically corroded by moisture inthe gas phase.

The invention also provides a system for monitoring a gas volume in aliquid-filled installation (9), in particular a transformer, comprisingat least one multi-chamber system, a liquid system and a device formonitoring the gas volume, in particular a Buchholz relay, theinstallation being connected via a liquid system to the device formonitoring the gas volume and to the multi-chamber system. According toone preferred embodiment, the multi-chamber system is arrangeddownstream of the device for monitoring the gas volume.

The use of the multi-chamber system as an expansion tank forliquid-cooled installations, in particular transformers, in a means oftransport is also advantageous. The use of the system for monitoring agas volume in a means of transport is also advantageous. Anapproximately leveled-out liquid column is no longer ensured in theexpansion tank when the means of transport accelerates, so that, as aresult, considerable pressure fluctuations can occur, and ambient aircan pass into the liquid cooling system. The multi-chamber systemaccording to the invention offers the advantage that it is also possibleto use a liquid system for a transformer in systems which are subject toacceleration such as, for example, a vehicle. The infiltration of air orgases from the outer region of the system is also prevented, even duringacceleration.

Further advantageous measures are described in the subclaims; theinvention is described in more detail in the following on the basis ofexemplary embodiments and the following figures, in which:

FIG. 1 is a schematic illustration of the multi-chamber system accordingto the invention;

FIG. 2 is a schematic illustration of the system according to theinvention for monitoring a gas volume in a liquid-filled installation.

FIG. 1 illustrates a multi-chamber system 1 according to the invention.

The first chamber 2 is arranged in the second chamber 3 and the twochambers 2, 3 are connected to one another by means of a second pipelinesystem 5. A first pipeline system 4 is connected to a liquid system 10.The first chamber 2 is completely filled with liquid, preferably with acooling liquid such as, for example, transformer oil. The secondpipeline system 5 is arranged in the first chamber 2 in such a way thatliquid can be moved between the first and second chambers 2, 3 only viathe upper opening of the second pipeline system 5, the opening beingarranged close below the top cover of the first chamber 2. In this case,a hydraulic connection is only produced between the second container 3and the cooling system via the liquid system 10 when the first chamber 2is completely filled with a liquid. Said design also prevents air orgases in the second chamber 3 passing into the first chamber 2 via thesecond pipeline system 5 and subsequently into the liquid system 10 viathe first pipeline system 4. The air dehumidifier 7 serves to reduce thedegree of humidity in the gas phase above the liquid surface.

According to the invention, at least one diaphragm 6 a, 6 b is alsoprovided which, in the second chamber 3, tightly and hermetically sealsoff the liquid from the gas phase. The diaphragm 6 a is fixed to theinner wall of the second chamber 3 by means of brackets 8. This preventsan infiltration of air or gases into the multi-chamber system 1 andtherefore the liquid system 10 even if the liquid columns in thepipeline systems “break down” as a result of external influences and airor gases can infiltrate the system. In this case, the elastic diaphragm6 a deforms corresponding to the liquid movements in the second chamber3, and therefore allows an equalization of the liquid within themulti-chamber system 1 and therefore the liquid system 10 without itbeing possible for air or gases to pass in. Said multi-chamber system 1according to the invention also prevents air or gases from the gas phaseof the second chamber 3 from diffusing into the liquid of the secondchamber 3.

The air dehumidifier 7 serves to reduce the degree of humidity of thegas phase above the liquid surface or above the diaphragm surface 6 a.

FIG. 2 is a schematic illustration of the system according to theinvention for monitoring a gas volume in a liquid-filled installation 9,for example a transformer. The gases produced in the liquid-filledinstallation 9 are conveyed onward in a liquid system 10 to a Buchholzrelay 11. The gas volume produced is monitored in the Buchholz relay.The multi-chamber system 1 is also coupled as an expansion tank to theliquid system. The position of the multi-chamber system 1 relative tothe transformer 9 or relative to the Buchholz relay 11 is arbitrary,since the pressure equalization in the second chamber 3 (notillustrated) takes place with the liquid system 10 as a result of ahydraulic connection. The system is therefore also suitable for use insystems which are subject to acceleration. Reference symbols 1.Multi-chamber system 2. First chamber 3. Second chamber 4 First pipelinesystem 5. Second pipeline system 6.a., 6.b. Diaphragm 7. Airdehumidifier 8. Diaphragm bracket 9. Liquid-filled installation 10.Liquid system 11. Device for monitoring a gas volume 12. Gas phase inthe second chamber

1-12. (canceled)
 13. A multi-chamber system forming a liquid expansiontank, comprising: a first pipeline system disposed in and connecting afirst chamber to a liquid system; a second pipeline system connectingsaid first chamber to at least one second chamber; wherein said secondpipeline system is arranged in said second chamber such that, whenliquid is present in said second chamber, a liquid pressure thusgenerated is also present in said second pipeline system; and whereinsaid second pipeline system is arranged in said first chamber such thatsaid second pipeline system is completely filled with a liquid, and ahydraulic connection is produced between said liquid system and saidsecond chamber, only when said first chamber is substantially completelyfilled with a liquid.
 14. The multi-chamber system according to claim13, wherein said second pipeline system has an opening disposed in anupper region of said first chamber.
 15. The multi-chamber systemaccording to claim 13, which comprises at least one diaphragm disposedin said second chamber for sealingly closing off a surface of the liquidfrom a gas phase in said second chamber.
 16. The multi-chamber systemaccording to claim 15, wherein said first chamber is disposed withinsaid second chamber, said first and second chambers being rotationallysymmetrical, and the surface of the liquid in said second chamber issealingly closed off from the gas phase in the second chamber by way ofa rotationally symmetrical diaphragm.
 17. The multi-chamber systemaccording to claim 15, wherein said diaphragm is an elastic diaphragm.18. The multi-chamber system according to claim 15, which comprisesbrackets on an inner wall of said second chamber fixing said diaphragm.19. The multi-chamber system according to claim 15, which comprisesguide rails, providing sealing closure, on an inner wall of said secondchamber for guiding said diaphragm corresponding to the liquid surfacein said second chamber.
 20. The multi-chamber system according to claim13, wherein at least one parameter of said pipeline systems, theparameters being selected from the group consisting of cross sectionsand height levels of said pipeline systems, is configured as a functionof a maximum possible liquid pressure in said first chamber.
 21. Themulti-chamber system according to claim 13, which comprises an airdehumidifier disposed to reduce a moisture in a gas phase in said secondchamber.
 22. A system for monitoring a gas volume in a liquid-filledinstallation, the system comprising: at least one multi-chamber systemaccording to claim 13; a liquid system communicating with said firstpipeline system; a monitoring device for monitoring a gas volume;wherein the liquid-filled installation is connected via a liquid systemto said monitoring device and to the at least one multi-chamber system.23. The system according to claim 22, wherein the liquid-filledinstallation is a transformer.
 24. The system according to claim 22,wherein said monitoring device is a Buchholz relay.
 25. The systemaccording to claim 22, wherein the multi-chamber system is disposeddownstream of said monitoring device or monitoring the gas volume. 26.In combination with a transportation device, the multi-chamber systemaccording to claim 13 configured as an expansion tank for aliquid-cooled installation in the transportation device.
 27. Thecombination according to claim 26, wherein the liquid-cooledinstallation is a transformer.
 28. In combination with a transportationdevice, a system for monitoring a gas volume in a liquid-filledinstallation of the transportation device, the system comprising: atleast one multi-chamber system according to claim 13; a liquid systemcommunicating with said first pipeline system; and a monitoring devicefor monitoring a gas volume; wherein the liquid-filled installation isconnected via a liquid system to said monitoring device and to the atleast one multi-chamber system.